For engineering and construction purposes, it is necessary to know the effective stress, or intergranular stress, of saturated soil. Conventional testing devices designed to measure effective stress do so indirectly by subtracting the pore pressure of the soil from the total pressure of the soil. Pore pressure is the pressure exerted by the water in the pores of the soil. Effective stress is the pressure exerted by the soil grains. Total pressure is the sum of pore pressure and effective stress. Such devices typically employ two diaphragms, one being deflected by the total pressure of the soil and the other being deflected by the pore pressure of the soil with the difference therebetween being equal to the effective soil stress. Such indirect measurements result in inaccuracies that lead to further complications when loads are to be placed on the soil.
It is also desirable to minimize the thickness of such an effective stress testing device so as to minimize the distrubance of the soil when the device is embedded therein for testing purposes. The need for two diaphragms increases the thickness of the testing device, thus increasing the disturbance of the soil and leading to further inaccuracies.
Therefore, a primary objective of the present invention is the provision of a device and process for directly measuring soil effective stress.
A further objective of the present invention is the provision of a device and process for mechanically measuring soil effective stress.
A further objective of the present invention is the provision of a device which utilizes a single diaphragm for measuring soil effective stress.
A further objective of the present invention is the provision of a device and process for accurately measuring soil effective stress.